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use futures_core::ready;
use futures_sink::Sink;
use pin_project_lite::pin_project;
use std::io;
use std::pin::Pin;
use std::task::{Context, Poll};
use tokio::io::AsyncWrite;
pin_project! {
/// Convert a [`Sink`] of byte chunks into an [`AsyncWrite`].
///
/// Whenever you write to this [`SinkWriter`], the supplied bytes are
/// forwarded to the inner [`Sink`]. When `shutdown` is called on this
/// [`SinkWriter`], the inner sink is closed.
///
/// This adapter takes a `Sink<&[u8]>` and provides an [`AsyncWrite`] impl
/// for it. Because of the lifetime, this trait is relatively rarely
/// implemented. The main ways to get a `Sink<&[u8]>` that you can use with
/// this type are:
///
/// * With the codec module by implementing the [`Encoder`]`<&[u8]>` trait.
/// * By wrapping a `Sink<Bytes>` in a [`CopyToBytes`].
/// * Manually implementing `Sink<&[u8]>` directly.
///
/// The opposite conversion of implementing `Sink<_>` for an [`AsyncWrite`]
/// is done using the [`codec`] module.
///
/// # Example
///
/// ```
/// use bytes::Bytes;
/// use futures_util::SinkExt;
/// use std::io::{Error, ErrorKind};
/// use tokio::io::AsyncWriteExt;
/// use tokio_util::io::{SinkWriter, CopyToBytes};
/// use tokio_util::sync::PollSender;
///
/// # #[tokio::main(flavor = "current_thread")]
/// # async fn main() -> Result<(), Error> {
/// // We use an mpsc channel as an example of a `Sink<Bytes>`.
/// let (tx, mut rx) = tokio::sync::mpsc::channel::<Bytes>(1);
/// let sink = PollSender::new(tx).sink_map_err(|_| Error::from(ErrorKind::BrokenPipe));
///
/// // Wrap it in `CopyToBytes` to get a `Sink<&[u8]>`.
/// let mut writer = SinkWriter::new(CopyToBytes::new(sink));
///
/// // Write data to our interface...
/// let data: [u8; 4] = [1, 2, 3, 4];
/// let _ = writer.write(&data).await?;
///
/// // ... and receive it.
/// assert_eq!(data.as_slice(), &*rx.recv().await.unwrap());
/// # Ok(())
/// # }
/// ```
///
/// [`AsyncWrite`]: tokio::io::AsyncWrite
/// [`CopyToBytes`]: crate::io::CopyToBytes
/// [`Encoder`]: crate::codec::Encoder
/// [`Sink`]: futures_sink::Sink
/// [`codec`]: tokio_util::codec
#[derive(Debug)]
pub struct SinkWriter<S> {
#[pin]
inner: S,
}
}
impl<S> SinkWriter<S> {
/// Creates a new [`SinkWriter`].
pub fn new(sink: S) -> Self {
Self { inner: sink }
}
/// Gets a reference to the underlying sink.
pub fn get_ref(&self) -> &S {
&self.inner
}
/// Gets a mutable reference to the underlying sink.
pub fn get_mut(&mut self) -> &mut S {
&mut self.inner
}
/// Consumes this [`SinkWriter`], returning the underlying sink.
pub fn into_inner(self) -> S {
self.inner
}
}
impl<S, E> AsyncWrite for SinkWriter<S>
where
for<'a> S: Sink<&'a [u8], Error = E>,
E: Into<io::Error>,
{
fn poll_write(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &[u8],
) -> Poll<Result<usize, io::Error>> {
let mut this = self.project();
ready!(this.inner.as_mut().poll_ready(cx).map_err(Into::into))?;
match this.inner.as_mut().start_send(buf) {
Ok(()) => Poll::Ready(Ok(buf.len())),
Err(e) => Poll::Ready(Err(e.into())),
}
}
fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
self.project().inner.poll_flush(cx).map_err(Into::into)
}
fn poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
self.project().inner.poll_close(cx).map_err(Into::into)
}
}
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